EvolutionBasics and Evidence
First, a Few Terms• Species A group of the same type of
organism that can interbreed and produce fertile offspring (humans are a species, homo sapiens)
• Population Group of the same species in a specific area
Evolution. What is it?
• Small or large genetic change at a population level inherited over several generations.
• Has to occur at the genetic level– Changes in allele frequency in a population over time
changes due to mutation and are passed along• Changes are seen in phenotypes (physical traits)• Descent with modification• Suggests common ancestor
EVIDENCE OF EVOLUTION
Anatomical Structures
Homologous Structures• If a bat, a human, an alligator, and a penguin
all evolved from a common ancestor, then they should share common anatomical traits
Vestigial Structures
• Body parts that seaming have no function• At one time in evolutionary history, they were
needed– Such as the pelvis of a whale, pelvic girdle in some
snakes, wisdom teeth• Leftovers from evolution• It used to be thought our appendix was vestigial,
however, it is thought that when beneficial bacteria in our gut is depleted, the appendix allows them to be re stored;
Biochemical (Molecular) Evidence
• Organisms that are more related have fewer differences in their amino acid sequences. (Cytochrome C below)
Fossils
• Fossils– Formed when organism dies is in silt, mud, sand or
clay soon after death– Sometimes an insect will die in tree sap (amber)
• Not all dead organisms will fossilize– The conditions have to be right!!
Example – Evolution of the Camel
Dinosaur National Monument: Fossilized dinosaur skeleton in sandstone
25.0 Fossil of a fish: perch
Dinosaur tracks (‘trace fossils’)
Barosaurus (27 m tall herbivore from late Jurassic (140 mya)
Leaf impression:Some fossils are imprints, some actually retain original organic matter
Petrified trees: Minerals dissolved in water seep into tissues of dead organisms, replace its organic material, and turn it to stone
Scorpion in hardened resin from a tree (whole organism preserved